This invention relates to concentric shafts for the high and low turbine/compressor of a twin spool turbine power plant and particularly to the intershaft bearing thereof.
The problem solved by this invention is the prevention of the rollers of a roller bearing assembly from loosening occasioned by the fact that the high compressor spool runs faster than the low compressor spool of a gas turbine engine so that obviously the difference in rotational speed causes a difference in the centrifugal loads acting on the inner and outer races such that one grows faster than the other hence causing the rollers to loosen.
We have found that we can improve this type of bearing by incorporating a ring fitted adjacent the outer race which ring is selected from material that exhibits a higher modulus of elasticity and lower coefficient of expansion that that exhibited from the material of the bearing. Satisfactory material for such a ring would be fabricated from a molybdenum or tungsten material or alloy thereof. For example an efficacious arrangement would be when the outer race has a coefficient of expansion of 6.times.10.sup.-6 and its modulus would be 30.times.10.sup.6 and the surrounding ring has a coefficient of expansion of 2.times.10.sup.-6 and its modulus of elasticity is 50.times.10.sup.6.